Self-propelled vehicle propelled by an elliptical drive train

ABSTRACT

A bicycle that includes an elliptical pedaling motion is provided. The bicycle includes a frame, having a front wheel and a rear wheel, and a first and a second foot link guide track. A first and a second foot link, each including a foot platform and a guide track coupler that slideably couples each foot link to a respective foot link guide track and a crank assembly that is coupled to the first and second foot links and to a sprocket that is rotatably coupled to the frame. This Abstract is provided for the sole purpose of complying with the Abstract requirement rules that allow a reader to quickly ascertain the subject matter of the disclosure contained herein. This Abstract is submitted with the explicit understanding that it will not be used to interpret or to limit the scope or the meaning of the claims.

Priority is claimed to provisional application Ser. No. 60/860,570,filed Nov. 21, 2006, entitled: A Two-Wheeled Human-Powered VehiclePropelled by an Elliptical Drive Train, which is referred to andincorporated herein in its entirety by this reference.

FIELD OF THE INVENTION

The present invention generally relates to bicycles. More particularly,the invention concerns a bicycle having an elliptical drive train.

BACKGROUND OF THE INVENTION

The most common human-powered vehicle is the bicycle. Use of the bicyclefor exercise, recreation, and transportation is well-known. Operators ofconventional bicycles are in a seated position and pedal in anessentially circular motion to perform the mechanical work necessary topropel the vehicle. During operation, the operator's upper body istypically bent forward at the waist and held in place by the muscles ofthe arms, shoulders, abdomen, and lower back. This most common ridingposition is relatively stressful. Bicycle riders often experience pain,discomfort, and/or numbness in the pelvic region from sitting on thebicycle seat or “saddle”, and discomfort in the lower back, arms, andshoulders from the bent-over riding position.

To alleviate the discomfort associated with prolonged use ofconventional bicycles, recumbent bicycles in which the operator propelsthe bicycle from a reclined position are known. Although recumbentbicycles alleviate much of the discomfort associated with conventionalbicycles, the reclined riding position makes these vehicles less stableand more difficult to ride. The recumbent bicycle is also limited as acommuter vehicle because the low-to-the-ground configuration allowsobstacles to easily obstruct the operator's line of sight and makes himor her less visible to other vehicles, cyclists, and pedestrians. Inaddition, because operators of conventional and recumbent bicycles areseated, they do not receive the musculoskeletal benefits ofweight-bearing exercise when operating these vehicles.

Therefore, there remains a need to overcome one or more of thelimitations in the above-described, existing art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of one embodiment of the bicycle;

FIG. 2 shows a side elevation view of the bicycle of FIG. 1, depictingschematically the elliptical pedaling profile;

FIG. 3 shows a side elevation view of the bicycle of FIG. 1, depictingschematically an operator's zone;

FIG. 4 shows a perspective view of another embodiment of the bicycle;

FIG. 5 shows a perspective view of yet another embodiment of thebicycle;

FIG. 6 shows a perspective view of yet another embodiment of thebicycle;

FIG. 7 shows a perspective view of yet another embodiment of the bicyclethat includes an adjustable guide track;

FIG. 8 shows a close-up perspective view of adjustable crank arms thatmay be coupled to the bicycle;

FIG. 9A shows a perspective view of one embodiment of an adjustable footplatform that may be coupled to the bicycle;

FIG. 9B shows a perspective view of another embodiment of an adjustablefoot platform that may be coupled to the bicycle;

FIGS. 10A-L show side elevation views of different embodiments of loadwheel retention devices that may be coupled to the bicycle;

FIG. 11 shows a perspective view of one embodiment of an adjustablesteering tube that may be coupled to the bicycle;

FIG. 12 shows a perspective view of one embodiment of a direct drivesystem that may be coupled to the bicycle;

FIG. 13A shows a perspective view of another embodiment of the bicyclethat includes a foldable frame;

FIG. 13B shows a perspective view of the bicycle depicted in FIG. 13Aafter it has been folded; and

FIG. 14 shows a perspective view of yet another embodiment of thebicycle.

It will be recognized that some or all of the Figures are schematicrepresentations for purposes of illustration and do not necessarilydepict the actual relative sizes or locations of the elements shown. TheFigures are provided for the purpose of illustrating one or moreembodiments of the bicycle with the explicit understanding that theywill not be used to limit the scope or the meaning of the claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the bicycle of the present invention. It will beapparent, however, to one skilled in the art that the bicycle may bepracticed without some of these specific details. For example, a varietyof load wheel retention devices may be employed. Throughout thisdescription, the embodiments and examples shown should be considered asexemplars, rather than as limitations on the bicycle. That is, thefollowing description provides examples, and the accompanying drawingsshow various examples for the purposes of illustration. However, theseexamples should not be construed in a limiting sense as they are merelyintended to provide examples of the bicycle rather than to provide anexhaustive list of all possible implementations of the bicycle.

The present disclosure relates generally to human-poweredtransportation, and more specifically to transport, exercise, andrecreational vehicles powered by an elliptical pedaling motion thatgenerally mimics the kinematics of walking or running. The apparatus, ofwhich one embodiment is a bicycle, described herein provides an improvedmeans of human-powered transportation that has advantages overconventional bicycles, scooters, upright step-cycles, and otherhuman-powered vehicles.

As defined herein, a “bicycle” is every vehicle propelled, at least inpart, by human power in the form of feet, or hands, acting upon pedals,having at least two wheels, except scooters and similar devices (whichare defined as vehicles operated by a foot contacting the ground). Theterm “bicycle” also includes three and four-wheeled human-poweredvehicles.

More specifically, disclosed herein is a low cross-over height bicyclepowered by an elliptical pedaling motion that generally mimics thekinematics of running or walking and provides a means of human-poweredtransportation that has advantages over conventional uprightstep-cycles, bicycles, and scooters. Also disclosed herein are methodsfor enabling the operator to adjust the pedaling profile of such avehicle.

An upright step-cycle is known in the art, but has several drawbacks.For example, the length of the wheelbase of several upright step-cyclesdescribed limits the means by which they can be transported in anothervehicle, such as a passenger car, and prevents them from being turnedaround on narrow bike paths or streets without the operator dismountingthe vehicles. Conventional upright step-cycles also have sprockets and achain positioned near the operator. If contacted, these moving parts candamage the operator's clothing and/or injure the operator. Furthermore,conventional upright step-cycles have frames that position supportstructures in the operator's zone, discussed in detail below. Framemembers located in the operator's zone are likely to injure the operatorif he or she contacts them while riding or during a fall. Frame memberslocated in the operator's zone also make mounting and dismounting thevehicle more difficult.

In addition, conventional upright step-cycles lack several features thatcould enable the operator to easily modify the vehicle's pedalingprofile and thereby allow a single vehicle to be adjusted to accommodatea wide range of different sized riders. As discussed above, the path ofmotion through which the operator's foot travels while pedaling thesevehicles is generally elliptical. Some people prefer this generallyelliptical motion to the generally circular motion used to propel aconventional or recumbent bicycle because the generally ellipticalmotion more closely mimics walking, running, or climbing and has beenshown to be a more effective means for strengthening the leg musclesthan cycling while avoiding much of the stress and impact generated byrunning. However, because the pedaling motion mimics human movement,operators with different anatomical dimensions will generally requiredifferent pedaling profiles. Specifically, a taller operator wouldlikely require a pedaling profile with a longer stride length than ashorter operator would. In addition, a more aggressive operator mightprefer a steeper foot platform take-off angle so that he or she couldgenerate more low-end torque, while a less aggressive rider might prefera flatter pedaling profile to reduce foot and knee flexion during thepedal stroke.

As discussed below, the shape of the pedal stroke is generallydetermined by the length of the crank arms, the length of the footlinks, the location of the foot platforms on the foot links, and theangle of the foot link guide tracks. Conventional upright step-cycleslack easy methods for adjusting the length of the crank arms and thelocation of the foot platforms. Enabling operators to easily optimizethe pedaling profile by adjusting these aspects of the propulsion systemwould enhance the functionality of an upright step-cycle.

Another form of human-powered transportation is the scooter.Conventional scooters are operated in a standing position. The operatorpropels a scooter forward by pushing one leg against the ground in arearward direction. Scooters have the advantage of being morecomfortable to ride than conventional bicycles without many of thedrawbacks of recumbent bicycles. Because the operator of a scooter ridesin an upright position, he or she does not experience the numbness andpain caused by sitting on a seat or saddle. In addition, the operator isless susceptible to shoulder and lower back pain because he or she isnot hunched over the handlebars. As compared to a recumbent bicycle, theoperator's standing position reduces the likelihood that his or her lineof sight will be obstructed and makes him or her more visible to othervehicles and pedestrians. A scooter is also more stable and easier toride than a recumbent bicycle, thereby reducing the frequency of fallingfor unskilled operators. Moreover, riding a scooter is a weight-bearingexercise that provides the operator with a means of strengthening theleg muscles and bones that is not available to operators of conventionaland recumbent bicycles.

However, the scooter does have disadvantages. Although an operator cantravel longer distances at higher speeds on a scooter than he or shegenerally could by walking or running, a scooter's propulsion mechanismis not very efficient, especially when compared to that of aconventional bicycle. As a result, scooters are generally not used forbusiness commuting, sustained exercise, or for other applications thatrequire long-distance or high-speed travel.

Mechanical devices that improve the efficiency of conventional scootersare known. A typical pedal-driven scooter is propelled forward by theoperator pumping one or two platforms up and down. Although thismechanism can be a more efficient means of propulsion than pushingbackwards against the ground, it is not ideal because it must betranslated into rotational motion to propel the vehicle forward. Thesemechanisms can also cause knee injuries because of the operator's needto reverse his or her leg's direction of motion at the top and bottom ofeach pedal stroke. Therefore, the introduction of a more efficient andlower impact scooter propulsion system would enhance the utility ofpedal driven scooters.

With reference now to the Figures, disclosed herein is anoperator-propelled vehicle in which rotation of left and right crankarms causes the respective left and right foot platforms to move alongan elliptical path. The term “elliptical” with regard to “ellipticalpedaling motion” or “elliptical pedaling profile” or “elliptical path”or “elliptical motion” is intended in a broad sense to describe a closedpath of motion having a relatively longer first axis and a relativelyshorter second axis (which extends perpendicular to the first axis as inan ellipse).

The embodiments shown and described herein are generally symmetricalabout a vertical plane extending lengthwise. Reference numerals aregenerally used to designate both the “right-hand” and “left-hand” parts,and when reference is made to one or more parts on only one side of theapparatus, it is to be understood that corresponding part(s) may bedisposed on the opposite side of the apparatus. The portions of theframe that are intersected by the plane of symmetry exist individuallyand thus, may not have any “opposite side” counterparts. Also, to theextent that reference is made to forward or rearward portions of theapparatus, it is to be understood that the drive arm assembly is movablein either of two opposite directions.

FIG. 1 shows a general embodiment of the apparatus, or bicycle 100. Theapparatus 100 generally includes a foot link assembly 105 movablymounted on a frame, or frame structure 110, on which a pair of wheels(front wheel 115, rear wheel 117) are mounted. Generally, each foot linkassembly 105 is moveably mounted to the frame 110 at its forward endwhere it is slideably coupled to a foot link guide track 255 and at itsrearward end where it is rotatably coupled to the crank assembly 215.

Generally, each foot link assembly 105 includes a foot link 205, eachwith a foot platform 210, and a load wheel 250. The foot platforms 210on which the operator stands are mounted on an upper surface of eachfoot link 205 near a forward end of each foot link 205. Below each footplatform 210 near the frontal section of each foot link is a load wheel250 that contacts a sloping foot link guide track 255. In the embodimentdepicted in FIG. 1, two foot link guide tracks 255 run parallel to eachother on either side of the longitudinal axis of the apparatus 100 andare integral with the frame 110. The load wheel 250 and bearings aremounted to a fixed axle to allow nearly frictionless linear motion ofthe foot links 205 along the foot link guide tracks 255 and providerotational freedom of the foot links 205 with respect to the foot linkguide tracks 255.

As shown in FIG. 2, during pedaling, the operator (not shown) uses hismass in a generally downward and rearward motion as in walking orjogging to exert a force on the foot platforms 210 and thereby, the footlinks 205. This force causes the load wheel to roll down the slope ofthe foot link guide track 255 towards the rear of the apparatus 100 androtate the crank arms 235 about the crank arm bearing 245, turning thedrive sprocket 240. As with conventional bicycles, rotating the drivesprocket 240 causes the rear wheel sprocket 135 to rotate because theyare linked by a chain or belt 130. It will be appreciated that the chainor belt 130 may also comprise a rotating shaft or other drive means.Rotating the rear wheel sprocket 135 causes the rear wheel 117 to rotatebecause the rear wheel sprocket is attached to the rear wheel hub 145.Rotating the rear wheel 117 provides motive force that enables theapparatus 100 to move along a surface. The apparatus 100 can employ a“fixed” or “free” rear wheel, as is known in the art. The apparatus 100can also employ a planetary gear hub having different gear ratios, asmanufactured by Shimano, Sturmey-Archer and others.

One feature of the apparatus, or bicycle 100 is that the pedaling motiondescribed above results in the operator's foot traveling in a shape thatcan be described as generally elliptical. Propulsion using an ellipticalpedaling motion, as opposed to an up and down pedaling motion or acircular pedaling motion, has the advantage of substantially emulating anatural human running or walking motion. Further, an elliptical pedalingmotion is a simpler and more efficient means to rotate the rear wheel117 than is, for example, a vertical pumping motion. Moreover, the majoraxis of the ellipse in an elliptical pedaling motion can be much longerthan the stroke length of a circular or vertical pumping pedalingmotion, allowing the operator to employ a larger number of muscle groupsover a longer range of motion during the pedal stroke than he or shecould employ in a circular or up and down pedaling motion.

As shown in FIG. 2, dashed line E depicts the generally elliptical paththat the ball of the operator's foot would take throughout the pedalingmotion. The region where the ball of the operator's foot contacts thefoot platform 210 is labeled as item F. The power stroke during forwardmotion is from front-to-back and follows the lower half of theelliptical path E. As the operator's foot moves rearward through thepower stroke of the described elliptical pedaling motion, the heelportion falls more quickly than does the toe portion. The return strokeduring forward motion is from back-to-front and follows the upper halfof the elliptical path E. As the operator's foot moves forward throughthe return stroke of the described elliptical pedaling motion, the heelportion of the foot rises more quickly than does the toe portion.

As illustrated in FIG. 2, the shape of the elliptical path E isgenerally defined by the following parameters: (1) the length of themajor axis A; (2) the length of the minor axis B; and (3) the major axisangle γ. The length of the major axis A is generally equal to the stridelength of the pedaling motion. The length of the minor axis B relativeto the length of major axis A generally determines the vertical lift ofthe operator's foot and angular foot plantar-flexion throughout thepedaling motion. Decreasing the ratio of A to B increases the verticallift of the operator's foot and increases the angular footplantar-flexion. Conversely, increasing the ratio of A to B reduces thevertical lift of the operator's foot and decreases the angular footplantar-flexion. As the ratio of A to B approaches infinity, theelliptical path E collapses into a straight line of length A andeliminates the vertical lift altogether.

The major axis angle γ of the ellipse reflects the incline angle of thepedaling motion. A major axis angle γ of zero degrees emulates naturalwalking or running motion on flat ground. Increasing the major axisangle γ emulates natural walking or running motion on an incline. Footlink guide track angle θ is the angle of the foot link guide track 255from horizontal and is generally parallel with the major axis angle γ.

The three parameters that govern the shape of the generally ellipticalpedaling path E (major axis A, minor axis B, and major axis angle γ,discussed above) are generally a function of the following frame anddrive mechanism dimensions: crank arm length C, foot link length D,crank pivot offset P, operator foot offset J, and foot link guide trackangle θ. Crank arm length C is the distance between the center of thecrank arm bearing 245 to the foot link bearing 220. Foot link length Dis the distance between the center of the load wheel 250 and the footlink bearing 220. Operator foot offset J is the distance from the centerof the load wheel 250 to the region where the ball of the operator'sfoot contacts the foot platform, point F. Foot link guide track angle θis the angle of the foot link guide track 255 from horizontal and isgenerally parallel with the major axis angle γ. As discussed below,modifying these parameters will change the elliptical pedaling profileexperienced by the operator.

As illustrated in FIGS. 1-7, the frame, or frame structure 110 of theapparatus 100 can be comprised of a variety of materials. FIG. 1 depictsone embodiment of the apparatus 100 in which the frame 110 is comprisedof a rigid tubular metal, such as aluminum, steel, or titanium. Asillustrated in FIG. 1, the frame structure 110 includes a lower framemember and two foot link guide tracks 255 that, in this embodiment, alsoact as structural frame members. FIG. 5 depicts an embodiment of theapparatus 100 in which the frame 110 is comprised of sheet metal, and inthis embodiment, one frame member may be the lower portion of the frame110 (nearest the ground) and a second frame member may be the foot linkguide track 255 that comprises an upper portion of the frame 110. FIG. 6depicts an embodiment of the apparatus 100 in which the frame 110 iscomprised of a graphite composite, and in this embodiment, similar tothe embodiment illustrated in FIG. 5, one frame member may be the lowerportion of the frame 110 (nearest the ground) and a second frame membermay be the foot link guide track 255 that comprises an upper portion ofthe frame 110, even though the two frame members may be formed together.

Other materials may also be used to construct the frame for theapparatus, such as plastics, alloys, other metals, etc. The frame 110provides the structural rigidity necessary to support the rider while heor she is operating the apparatus 100. The frame 110 also connects themovable portions of the apparatus 100 together into a complete system.

One of the features common to all of the proposed embodiments ofapparatus 100 is a low cross-over height frame. As defined herein, aframe has a low cross-over height if there are no structural framemembers positioned in the operator's zone. Generally, the operator'szone is the area of space occupied by the operator when riding theapparatus. For example, one embodiment of the operator's zone isillustrated in FIG. 3, and comprises an area defined by points K and L,and line N. Point K is the aft-most position of the load wheel 250,point L is the mid-point of travel of the load wheel 250, and line N isformed by a line that extends between the tops of the front wheel 115and rear wheel 117. During operation, the load wheel 250 travels from aforward-most position 103 to a rear-most, or aft-most position K. Asshown in FIG. 3, the mid-point of travel for the load wheel 250 is pointL, which is half the distance of the load wheel total distance of travel107. Put differently, the load wheel total distance of travel 107 is themaximum stride length that an operator would be able to achieve, and mayrange from about 14 inches to about 26 inches. As shown in FIG. 3, theoperator's zone extends from line N upwards, and is bounded by twosubstantially vertical lines that extend from points K and L.

It will be appreciated that the operator's zone may extend furtherforward or backward depending on the amount of forward and rearwardmovement the operator must undertake when operating a specificembodiment of the apparatus. For example, for some embodiments, point Lmay be defined as the location of the ball of the operator's foot whenit is located at the forward extreme of the pedal stroke (point 103) onthe foot platform 210, and point K may be defined as the heel of theoperator's foot when it is on the foot platform 210 and the load wheel250 is at its aft-most position. Similarly, it may be appreciated thatfor embodiments where the front wheel 115 and the rear wheel 117 aresmall (have diameters less than 20 inches), line N may be set at a givendistance off of the ground (approximately 26 inches) rather than formedby a line that extends between the tops of the front wheel 115 and rearwheel 117.

FIGS. 1, 4, 5, 6, 7, 12, 13, and 14 depict several different proposedembodiments, all of which have low cross-over height frames 110. Asshown in FIG. 3, generally, the frame 110 includes truss members 112 andtwo foot link guide tracks 255. However, some frame 110 embodiments,like those shown in FIGS. 5 and 6, do not include truss members 112.Moreover, the foot link guide tracks 255 may be an integral component ofthe frame, as shown, for example, in FIGS. 4-6. The individual guidetracks may also be integrated together to form a single guide track, asdepicted in FIG. 14.

Low cross-over height frames 110 are safer and more convenient to usethan conventional upright step-cycle or bicycle frames. The lowcross-over height design is safer because there are no supportstructures in the operator's zone that could cause injury during a fallor during riding. These frames are also more stable to ride because theyhave a lower center of gravity. The low cross-over height design alsomakes the apparatus 100 easier and safer to mount and dismount becausethere are no support structures in the operator's zone to step over oraround when mounting or dismounting. In addition, the low cross-overheight makes the apparatus 100 easier to maneuver in tight spacesbecause it enables the operator to easily step across the apparatus 100,which facilitates moving the apparatus 100 into and out of storageareas, trains, buildings, and the like.

One consideration when designing low crossover-height frames 110 isstiffness in bending. Unlike conventional frames, a low cross-overheight frame 110 does not include a structural member above the plane ofthe top of the wheels to provide stiffness in bending. Because the frame110 must support the dynamic weight of the operator during riding,stiffness in bending is important not only to prevent frame memberfailure, but also to improve pedaling efficiency and handling.

The proposed embodiments have been designed to provide sufficient frame110 stiffness in bending. For example, the frame 100 design in FIG. 4has a stiffness of approximately 2500 lbf/in. When the embodimentdepicted in FIG. 4 is subjected to a 200 pound load in the center of thefoot link guide tracks 255, the frame 110 will deflect no more thanabout 0.08 inches, thereby minimizing the negative effects of frameflexing discussed above. This improved stiffness in bending is achievedby several features contained in the low cross-over height frame 110,including incorporation of the foot link guide tracks 255 into the frame110 as frame members, and the use of truss members 112 to enhancestiffness.

As shown in several of the Figures, embodiments of the apparatus 100include a steering mechanism 120 that may comprise handlebars 119, asteering wheel (not shown), or other steering means. The steeringmechanism 120 can be mounted upon a fixed or adjustable steeringextender 125 that extends upward from the frame 110. The steeringmechanism 120 can be telescopically adjustable, as well as adjustableforward and backward, and can incorporate a pivot to provide rotationaladjustability. One feature is that an adjustable steering mechanism willpermit easy and safe use by a variety of operators having differentheights and arm dimensions.

FIG. 11 depicts a detailed view of one embodiment of a telescopingsteering mechanism. In this embodiment, the steering extender 125 isheld by a steering extender sleeve 126. The inside diameter of thesteering extender sleeve 126 is larger than the outside diameter of boththe front fork steer tube 127 and the steering extender 125. In thisembodiment, the front fork steer tube 127 has been inserted into thebottom of the steering extender sleeve 126 and is clamped to it by meansof one or more fasteners 128, such as a bolt and nut, pin, clip or othermeans. In addition, the steering extender 125 is inserted into the topof the steering extender sleeve 126 and is clamped to it by means ofanother fastener 128. The height of the steering mechanism 120 can beadjusted by varying the position where the steering extender sleeve 126clamps to the steering extender 125. FIGS. 13A-B depict a steering tubeassembly with both translational and rotational adjustability.

As shown in FIGS. 1, 4, and 6, embodiments of the apparatus 100 can alsoincorporate a rear wheel cover 190. The purpose of the rear wheel cover190 is to prevent the operator's legs, feet, clothing, and other objectsfrom contacting the rear wheel 117. The cover 190 can be made frommetal, plastic, graphite composite, fiberglass, or other materials. Itcan be attached to the frame by bolts, welds, brazes, or other methods,or it can be an integrated part of the frame 110 as shown in FIG. 6. Tofacilitate transporting and maneuvering the apparatus 100 while walking,a handle 191 can be attached to, or incorporated into, the rear wheelcover 190, or a handle 191 can be attached to, or incorporated into, theframe 110 and protrude through an opening in the rear wheel cover 190.

FIG. 1 depicts a rear wheel cover 190 with a handle 191. The handle 191is integrated into the rear wheel cover 190 and the rear wheel cover 190is bolted to the frame 110. FIG. 4 depicts a rear wheel cover 190without a handle that is bolted to the frame 110. FIG. 6 depicts a rearwheel cover 190 without a handle that is integrated into a carbon fiberframe 110.

Referring now to FIGS. 10A-B, each foot link 205 can be laterallyconstrained onto its respective foot link guide track 255 in a varietyof ways. FIGS. 10A and 10B, which is a sectional view about section M-Mshown in FIG. 10A, and FIGS. 10C and 10F depict one method of laterallyconstraining the foot link 205. In this method, the load wheel 250 has aV-groove 305 that mates to the counterpart geometry of a substantiallydiamond-shaped foot link guide track 255. The top of the foot link guidetrack 255 fits into the center of the groove of the load wheel 305,thereby laterally constraining the foot link 205.

FIGS. 10D, 10 i, 10J, and 10K depict a similar mechanism for laterallyconstraining a foot link 205 onto a round or tubular-shaped foot linkguide track 255. In these embodiments, the contact surface of the loadwheel 250 has a concave shape that mates with the counterpart geometryof the round foot link guide track 255. The top of the foot link guidetrack 255 aligns with the center of the load wheel 250 and the foot link205 is laterally constrained onto the foot link guide track 255 by theinterface of the concave load wheel 205 and the round tube comprisingthe foot link guide track 255.

FIG. 10E depicts another method of laterally constraining a foot link205 onto a foot link guide track 255. This embodiment uses a load wheelcarrier 271 that is attached to each foot link 205. In the depictedembodiment, the load wheel carrier 271 holds two load wheels 250. Theload wheels 250 are set into the load wheel carrier 271 at opposingangles. The interaction of each load wheel 250 with the foot link guidetrack 255 results in the lateral constraint of the attached foot link205. Although a diamond shaped foot link guide track 255 is depicted inFIG. 10E, this method could also be used with round, tubular, orsimilarly shaped foot link guide tracks 255.

The lateral constraining methods discussed above are intended to preventthe foot link assembly from laterally disengaging with, or “falling off”of, the foot link guide track 255. The list is not intended to beexhaustive. Its purpose is only to illustrate a few of the many methodsof restraining the foot links 205 in the lateral direction.

In addition to lateral constraint, each foot link 205 may also beretained in the normal direction (i.e., a direction generallyperpendicular to the foot link guide track 255). That is, each foot link205 may be restrained from “jumping off” the foot link guide track 255.The foot links 205 could be subject to disengaging in the normaldirection whenever, for instance, the apparatus 100 travels over sharplyundulating or rough terrain, or strikes an obstacle. The retentionmethods discussed below are intended to prevent the foot link assemblyfrom disengaging with the foot link guide track 255 in the normaldirection during operation of the apparatus 100. The list is notintended to be exhaustive. Its purpose is only to illustrate a few ofthe many methods of restraining the foot links 205 in the normaldirection.

FIGS. 10A, 10B, 10C, 10D, 10E, 10F, and 10 i depict a method of normalretention in which one or more retaining links 605 holds a retainingmember 610 underneath a feature of the foot link guide track 255, or thefoot link guide track 255 itself. The interaction of the retainingmember 610 with the foot link guide track 255 or a feature on the footlink guide track 255 prevents the load wheel 250 from disconnecting withthe foot link guide track 255.

There are many ways to vary this method of retention, including changingthe shape, size, number or other characteristic of the retaining links605, changing the shape, size, number, or other characteristic of theretaining member 610, changing the shape, size, or number of foot linkguide tracks 255, or changing the shape, size, number, or othercharacteristics of features connected to the foot link guide track 255or frame 110. For example, FIGS. 10F and 10 i depict just two kinds ofthe many features that could be attached to the foot link guide tracks255 to facilitate retention. FIG. 10F depicts an eave-like structure,and FIG. 10 i depicts a rail-like structure. A variety of other featurescould be employed for this purpose. Similarly, FIGS. 10A and 10D depictdifferent shapes of the retaining member 610. FIG. 10A shows a roundmember and FIG. 10D shows a cylindrical member. In fact, the retainingmember 610 could be any manner of bar, pin, wheel, cable, or othermechanism that could serve to prevent the load wheel 250 fromdisengaging with the guide track 255.

Moreover, the retaining link 605 or links can be designed to either holdthe retaining member 610 at a fixed distance from the load wheel, or toallow for adjustment of that distance. FIGS. 10C, 10D and 10E depictretaining links 605 that hold the retaining member 610 at a fixeddistance. FIG. 10B depicts one embodiment of a retaining link 605 inwhich a preloaded spring mechanism 630 holds the retaining member 610 incontact with the guide track 255 throughout the pedal stroke. Thepreloaded force can be adjusted by rotating the set screws 615 and 620.This same system could also be used to establish and then adjust a gapbetween the retaining member 610 and the guide track 255, therebypreventing the retaining member from contacting the guide track 255except when needed to prevent the load wheel from disengaging with theguide track 255. Such a gap can be set by rotating the set screws 615and 620. The gap can then be adjusted over time in the same manner tocompensate for wear of the load wheel 250. Again, the depictionsdescribed herein are meant to be illustrative only, and the apparatus100 may include any number of variations and embodiments relating toretention of the load wheel 250 to the foot link guide track 255.

FIGS. 10G, 10H, 10J and 10K illustrate several embodiments of an axlebar retention system. In this system, a retention member is passedthrough the axle of the load wheel such that it protrudes from one orboth ends of the axle. The load wheel is constrained in the normaldirection by the interface of this retention member and a structureattached to the frame 110. The retention member can be any manner ofpin, bolt, bar, or the like.

For example, as shown in FIGS. 10G and 10H, the axle retention member1010 protrudes from both sides of the load wheel 250. In FIG. 10G, eachend of the axle retention member 1010 passes through a slot 285 formedin the foot link guide track 255. The interaction between the axleretention member 1010 and the slot 285 prevents the foot link 205 fromdisengaging with the foot link guide track 255 in the normal direction.Similarly, in FIG. 10H, each end of the axle retention member 1010 ispositioned below a ledge 280 included in the foot link guide track 255.The interaction between the axle retention member 1010 and the ledge 280prevents the foot link 205 from disengaging with the foot link guidetrack 255 in the normal direction.

In FIGS. 10J and 10K, only one end of the axle retention member 1010protrudes from the load wheel 250. In FIG. 10J, the protruding end ofthe axle retention member 1010 has a hole drilled through it. The holecaptures a securing member 287 that is connected to the foot link guidetracks 255 or another part of the frame 110. The securing member 287 canbe any manner of rod, cable, bar, or similar item. Similarly, in FIG.10K, the axle retention member 1010 is slotted to capture a securingmember 287 that is connected to the foot link guide tracks 255 oranother part of the frame 110. In both embodiments, the interactionbetween the retention member 1010 and the securing member 287 preventsthe foot link 205 from disengaging with the foot link guide track 255 inthe normal direction.

FIG. 10L depicts an alternative embodiment that provides both lateraland normal constraint. In this embodiment, the load wheel 250 has beenreplaced by a linear bearing 1030. The linear bearing 1030 is free toslide along the foot link guide track 255, however the lower portion1020 of the linear bearing 1030 captures the foot link guide track 255,thereby preventing the foot link 205 from disengaging from the foot linkguide track 255 in the lateral or normal direction.

As discussed above, there are several ways to modify the ellipticalpedaling profile of the apparatus 100. One method is to change thelocation of the ball of the operator's foot (identified as location F inFIGS. 2, and 9A-B) with respect to the load wheel 250 or the first endof each foot link 205. Referring now to FIGS. 9A-B, the first end of thefoot link 205 is the end of the foot link 205 that is directly adjacentto the load wheel 250, and the second end of the foot link 205 is theend of the foot link 205 that is directly adjacent to the foot linkbearing 220 (shown in FIG. 1). Modifying the location of the operator'sfoot 121 relative to the load wheel 250 or the first end of the footlink 205 changes the operator foot offset (identified as distance J inFIGS. 2 and 9A-B). To achieve a flatter and more eccentric pedalingprofile, the operator can position his or her foot closer to the firstend of each foot link 205. Alternatively, by positioning his or her footfurther away from the first end of the foot link 205, the operator cancreate a more circular and less eccentric pedaling profile. Because thedistance between the operator's foot 121 and the load wheel 250 or firstend of each foot link 205 influences the pedaling profile, therepeatability of adjustments to this distance ensures that the operatorcan experience the desired pedaling profile.

There are a variety of ways to enable the operator to repeatably modifythe position of his or her foot relative to the first end of the footlink 205. FIG. 9A depicts one method. In this embodiment, each footplatform designates a single position for an operator's foot 121. Theinterface between each foot platform 210 and its respective foot link205 is adjustable such that the foot platforms 210 can be attached ontothe foot links 205 at different distances from the first ends of thefoot links 205. The attachment method in this embodiment is a pair ofreleasable clamps 905 that connect each foot platform 210 to itsrespective foot link 205. This mechanism enables the operator to adjusteach foot platform to achieve a repeatable placement of his or her footrelative to the first end of each foot link. In addition, each footplatform 210 could also include one or more securing elements 910 suchas ridges or straps to prevent the operator's foot 121 fromunintentionally disengaging from the foot platform 210. It will beappreciated that the securing elements 910 can take many equivalentforms, such as baskets, clips, bumps, cleats, or the like. In addition,index lines (not shown) could be incorporated into the foot link 205 tofacilitate more accurate and repeatable positioning of the footplatforms 210 relative to the first end of the foot link 205.

There are additional ways to create a repeatable adjustable interfacebetween the foot platforms 210 and foot links 205. For example, arepeatable interface could also be created by a series of mounting holesin the foot links 205 and/or the foot platforms 210 that allow fordifferent mounting positions of the foot platform 210 along the footlink 205.

FIG. 9B depicts an alternative method for enabling the operator torepeatably change the position of his or her foot relative to the firstend of each foot link 205. In this embodiment, the foot platform 210 islarge enough to permit the operator to change the position of his or herfoot relative to the first end of the foot link 205 without moving thefoot platform 210. The foot platform 210 includes one or more footlocators 920 to enable the repeatable use of the various foot positionson the foot platform 210. The foot locators 920 could include featuressuch as cleats, bumps, ridges, or the like. Each foot platform 210 couldalso include securing elements 910 as discussed in connection with FIG.9A.

As discussed above, another method for adjusting the pedaling profile ismodifying the length of the crank arms 235. As shown in FIGS. 1 and 8,the crank assembly 215 includes a crank extender 230 rotatably connectedto the second end of the foot link 205 at the foot link bearing 220. Thecrank assembly 215 also includes a crank drive arm 235 rotatablyconnected at the crank arm bearing 245 to a drive sprocket 240. As shownin FIG. 2, Circle R, shown as a dashed line, is generated by rotatingthe crank assembly 215 around the crank arm bearing 245. The distancebetween the center of the crank arm bearing 245 and the center of thefoot link bearing 220 is crank arm length C. Shortening crank arm lengthC will shorten the stride length A. Correspondingly, increasing crankarm length C will increase stride length A. Therefore, adjustments incrank arm length C can be made to modify stride length A to allowoperators of different stature to adjust the apparatus 100 to suit theirindividual dimensions.

There are many ways to modify the length of the crank arms 235. FIG. 8depicts one method for making the crank assembly 215 adjustable. Thismethod employs a slot-bolt assembly 810 where the crank extender 230includes a slot 270 and the crank drive arm 235 includes aperturesconfigured to receive crank fasteners 275 that can locate the crankdrive arm 235 at any position along slot 270. The crank extender 230 canthereby telescope, or adjust its length with respect to the crank drivearm 235.

There are additional ways to make the crank assembly 215 adjustable. Forexample, the slot-bolt assembly 810 discussed above can be replaced by aclamp with pins that can clamp the crank extender 230 to the crank drivearm 235 at various positions. Another embodiment may make the crankassembly 215 adjustable by incorporating a series of holes in the crankextender 230 or the crank drive arm 235, or both. In such an embodiment,the length of the crank drive 235 arms may be modified by changing whichholes are used to fasten the crank extender 230 to the crank drive arm235.

As discussed above, and again with reference to FIG. 2, crank arm lengthC is a significant factor that determines major axis length A, whichapproximately equals the stride length of a given pedaling profile. Fora rider of average height and body dimensions, as the stride lengthshrinks below approximately 17 inches, the rider's ability to transferpower to the apparatus 100 for purposes of acceleration and climbingbecomes reduced. As a result, while embodiments with stride lengthsgenerally less than about 17 inches may be appropriate for a smallpercentage of operators, the vast majority of riders will desire stridelengths longer than 17 inches to achieve sufficient pedaling efficiency.Embodiments of the apparatus 100 presented herein can accommodate stridelengths in excess of 23 inches.

As the stride length increases, it may be desirable to increase thewheelbase W as shown in FIG. 2. For a low cross-over height frame 110,the longer the wheelbase W, the more difficult it is to maintain anappropriate level of bending stiffness, yet a wheelbase W that issignificantly longer than conventional bicycles is desirable. Forexample, a conventional bicycle may have a wheelbase of about 40 inches,but embodiments of the present invention may have a wheelbase W that mayrange from about 55 inches to about 65 inches. As discussed above,embodiments of the apparatus 100 include a frame 110 having a sufficientbending stiffness to accommodate a stride length beyond 23 inches.

Alternative embodiments of the apparatus 100 can incorporate additionalfeatures, such as a direct drive propulsion mechanism, adjustable guidetracks, and/or foldability. FIG. 12 depicts an embodiment of theapparatus that employs a direct drive propulsion system. In thisembodiment, the crank arms 235 are connected directly to the hub 1210 bymeans of bearings (not shown) mounted in the frame 110, through whichpasses a linkage from each crank arm 235 to the hub 1210. Thisalternative embodiment alleviates the need for a chain and sprockets.This embodiment could incorporate a gearing system in thecrank-to-hub-wheel linkage that could allow the rear wheel to rotatemore quickly than the crank arms. Such a gearing system could provide afixed input-output ratio, or could allow for one of a series of gears tobe selected by the operator. In addition, the rear wheel 117 could beenlarged to allow the operator to achieve a greater rate of speed foreach completed pedal stroke.

FIG. 7 depicts a low cross-over height frame 110 with adjustable footlink guide tracks 255. The forward end of each foot link guide track 255is attached to a foot link guide track support 705 by the use of arotary bearing 710, so that the forward end of the foot link guide track255 can rotate about the foot link guide track support 705. Each footlink guide track support 705 is attached to its respective side of acollar 715 by the use of a bolt and low friction washers, or othersuitable means. The collar 715 can be clamped to the downtube 725 atvarious locations by means of bolts or other fasteners. The low frictionwashers allow each foot link guide track support 705 to rotate about thebolt. The rearward or second end of each foot link guide track 255 isattached to the frame by the use of a rotary bearing 720. Unclamping thecollar 715 allows the operator to slide the collar 715 along thedowntube 725, thereby adjusting the angle of the foot link guide tracks255. As discussed below, changing the angle of the foot link guidetracks 255 modifies the elliptical pedaling profile experienced by theoperator.

FIGS. 13A and 13B depict an embodiment of the apparatus 100 that can befolded to facilitate transport or storage in small spaces. In thisembodiment of a foldable apparatus 100, the apparatus 100 is foldedaccording to following procedure. First, the foot link retainer 610 oneach foot link assembly 105 is released from the guide track 255 byremoving a pin (not shown). Next, each foot link assembly 105 is rotatedabout its respective foot link bearing 220 towards the rear wheel 117approximately one hundred eighty (180) degrees. Next, the coupling 1340on each side of the apparatus is released. Each foot link guide track255 is then rotated downwards about guide track pivot 1330. Next, thecrank assembly 215 is rotated forward about pivot 1320 until the rearwheel 117 passes through the frame 110. Next, each guide track 255 isrotated upwards about guide track pivot 1330. Then the crank assembly215 is rotated until the right crank arm 235 points to the rear, asdepicted in FIG. 13B. At that point, each foot link 205 may be strappedto the adjacent crank arm extender 230. The right foot link assembly 105is then positioned on top of the front fork 127 and the left foot linkassembly 105 is positioned on top of the axle of the rear wheel 117.Next, the steering assembly pivot 1310 is released and the steeringextender sleeve 126 is rotated rearward. The steering extender sleeve126 is then locked in place at steering assembly pivot 1310 as depictedin FIG. 13B. Once locked, the steering extender sleeve 126 may be usedas a handle to carry or help direct the path of travel for the foldedapparatus 100. FIG. 13B depicts the results of following the foldingprocedure described above.

In addition, the apparatus 100 can include gearing. Gearing can beimplemented through techniques known in the art, including a series ofdifferent sized sprockets attached to the rear wheel 117 and selected bya derailleur, or a single rear sprocket connected to a hub that containsa series of gears inside of it which enable the hub to produce a varietyof input-to-output ratios. This embodiment could incorporate techniquesknown in the art to permit the operator to select gears. This couldinclude mounting a shift lever on the steering mechanism 120 as is knownin the art. The apparatus 100 can also include a fixed gear system withno freewheel on the rear wheel 117.

The apparatus can also include mechanisms to retard motion, such as rimor disc braking systems known in the art. These mechanisms can belocated on the front and/or rear wheels. The braking mechanisms can beactuated by, for example, a hinged handle or other structure mounted onthe handlebars to which the brake cables or some other mechanism areconnected, as is known in the art. In addition, the apparatus caninclude other attributes that are commonly incorporated onto other humanpowered vehicles, such as reflectors, lights, bottle cages, etc.

It is to be noticed that the term “comprising”, used in the claims,should not be interpreted as being limitative to the means listedthereafter. Thus, the scope of the expression “a device comprising meansA and B” should not be limited to devices consisting only of componentsA and B. It means that with respect to the present invention, the onlyrelevant components of the device are A and B. Moreover, the componentsA and B should not be limited to a specific relationship or form;instead, they can be integrated together into a single structure or canoperate independently.

Similarly, it is to be noticed that the term “coupled”, also used in theclaims, should not be interpreted as being limitative to directconnections only. Thus, the scope of the expression “a device A coupledto a device B” should not be limited to devices or systems whereindevice A is directly connected to device B. It means that there exists apath between A and B which may be a path including other devices ormeans. In addition, “coupled” does not necessarily mean “in a fixedposition or relationship” as “coupled” may include a moveable, rotatableor other type of connection that allows relative movement between A andB. Finally, “coupled” may also include “integral” where device A anddevice B are fabricated as an integral component or single structure.

Thus, it is seen that a bicycle is provided. One skilled in the art willappreciate that the bicycle of the present invention can be practiced byother than the above-described embodiments, which are presented in thisdescription for purposes of illustration and not of limitation. Thespecification and drawings are not intended to limit the exclusionaryscope of this patent document. It is noted that various equivalents forthe particular embodiments discussed in this description may practicethe invention as well. That is, while the bicycle has been described inconjunction with specific embodiments, it is evident that manyalternatives, modifications, permutations and variations will becomeapparent to those of ordinary skill in the art in light of the foregoingdescription. Accordingly, it is intended that the bicycle embrace allsuch alternatives, modifications and variations as fall within the scopeof the appended claims.

1. An apparatus, comprising: a frame structure; a steering mechanismcoupled to the frame structure; a front wheel and a rear wheel coupledto the frame structure, the rear wheel including a rear wheel axle; anoperator zone comprising an area located above a top of both the frontand rear wheels, and between an aft-most, and a mid-point of a loadwheel travel range, the operator zone not including any frame structure;and a first and a second foot link, with a first end of each foot linkcoupled to the frame structure, and a second end of each foot linkcoupled to a respective one of a first and a second crank arm, with eachcrank arm coupled to the rear wheel axle.
 2. The apparatus of claim 1,further comprising a first and a second foot platform, coupled to arespective one of the first and second foot links, with each footplatform including at least two positions for a foot of an operator. 3.The apparatus of claim 1, further comprising a first and second footplatform, coupled to a respective one of the first and second footlinks, where a position of either foot platform is adjustable relativeto its respective foot link.
 4. The apparatus of claim 1, where thesteering mechanism further comprises a pivot to pivot the steeringmechanism toward the operator zone.
 5. The apparatus of claim 1, wherethe frame structure further comprises a pivot to pivot the rear wheeltoward the operator zone.
 6. The apparatus of claim 1, furthercomprising a rear wheel cover sized to cover a portion of the rearwheel, the rear wheel cover including a handle sized to receive a humanhand.
 7. The apparatus of claim 1, where a length of each crank arm isadjustable.
 8. The apparatus of claim 1, where the frame structurecomprises at least one foot link guide track that receives at least oneof the first and second foot links, where a position of the at least onefoot link guide track is adjustable.
 9. The apparatus of claim 1,further comprising a first and a second load wheel, coupled to arespective one of the first and second foot links, each load wheelcoupled to a foot link guide track, where the foot link guide trackcomprises a portion of the frame structure.
 10. The apparatus of claim8, further comprising a collar adjustably coupled to the framestructure, with the at least one foot link guide track coupled to thecollar, the collar enabling a variation of a position of the foot linkguide track.
 11. The apparatus of claim 1, where a substantial portionof the frame structure comprises a sheet metal.
 12. The apparatus ofclaim 1, where the first and second crank arms are coupled to the rearwheel axle without a chain or a belt.
 13. An apparatus, comprising: aframe comprising at least one foot link guide track; a steeringmechanism coupled to the frame; a front wheel and a rear wheel coupledto the frame; a first and a second foot link coupled to the frame, eachfoot link including a guide track coupler that couples each foot link tothe foot link guide track and inhibits each foot link from disengagingfrom the foot link guide track; and a crank assembly coupled to thefirst and second foot links.
 14. The apparatus of claim 13, furthercomprising an operator zone comprising an area located above a top ofboth the front and rear wheels, and between an aft-most, and a mid-pointof a load wheel travel range, the operator zone not including any framestructure.
 15. The apparatus of claim 13, further comprising a first anda second foot platform coupled to a respective one of the foot links,where each foot platform enables a foot of an operator to be placed inat least two positions.
 16. The apparatus of claim 13, where thesteering mechanism further comprises a pivot to pivot the steeringmechanism toward the operator zone.
 17. The apparatus of claim 13, wherethe frame further comprises a pivot to pivot the rear wheel toward theoperator zone.
 18. The apparatus of claim 13, further comprising a rearwheel cover sized to cover a portion of the rear wheel, the rear wheelcover including a handle sized to receive a human hand.
 19. Theapparatus of claim 13, where a position of at least one foot link guidetrack is adjustable.
 20. The apparatus of claim 13, where the crankassembly includes a crank arm and a length of each crank arm isadjustable.
 21. The apparatus of claim 13, where a portion of the footlink guide track is substantially “V” shaped, and each guide trackcoupler comprises a rotatable wheel having a substantially similar “V”shape for rotatably mating thereto.
 22. The apparatus of claim 13, wherea portion of the foot link guide track has a substantially convexsurface, and each guide track coupler comprises a rotatable wheel havinga substantially concave surface for rotatably mating thereto.
 23. Theapparatus of claim 13, where each guide track coupler comprises arotatable wheel and a retention mechanism that inhibits the rotatablewheel from departing the foot link guide track by contacting a surfaceof the guide track or a surface coupled to the guide track.
 24. Theapparatus of claim 13, where a portion of each foot link guide track issubstantially “U” shaped, and each guide track coupler comprises arotatable wheel that rotatably engages a bottom of the “U” and aretention member that substantially engages a surface coupled to theguide track.
 25. The apparatus of claim 13, where each guide trackcoupler comprises at least one retention member structured tosubstantially engage a surface coupled to the foot link guide track. 26.The apparatus of claim 25, where each guide track coupler comprises aretention link coupled to the at least one retention member, and theretention link is adjustable to vary a position of the retention memberrelative to the surface coupled to the foot link guide track.
 27. Theapparatus of claim 25, where each guide track coupler comprises apreloaded retention link coupled to the at least one retention member,where the preloaded retention link locates the retention membersubstantially in contact with the surface coupled to the foot link guidetrack.
 28. The apparatus of claim 13, where each guide track couplercomprises a linear bearing that slides along the foot link guide track.29. An apparatus, comprising: a frame comprising a first and a secondfoot link guide track; a front wheel and a rear wheel coupled to theframe; a steering mechanism coupled to the frame; a first and a secondfoot link coupled to a respective one of the foot link guide tracks; anda first and a second foot platform, each respectively coupled to one ofthe foot links, where each foot platform comprises at least tworepeatable operator foot positions on each foot link.
 30. The apparatusof claim 29, where each foot platform has at least one repeatableoperator foot position and is movable along its respective foot link.31. The apparatus of claim 29, where each foot platform includes a footlocator structured to provide at least two repeatable operator footpositions on each foot platform.
 32. The apparatus of claim 29, furthercomprising a retention mechanism coupled to each foot platform, wherethe retention mechanism inhibits each operator foot from disengagingfrom its respective foot platform.
 33. An apparatus, comprising: aframe; a steering mechanism coupled to the frame; a front wheel and arear wheel coupled to the frame, the rear wheel including a rear wheelaxle; and a first and a second foot link, with a first end of each footlink coupled to the frame, and a second end of each foot link coupled toa respective one of a first crank arm and a second crank arm, with eachcrank arm coupled to the rear wheel axle, and a length of each crank armis adjustable.